Depositing conformal boron nitride films

ABSTRACT

A method of forming a boron nitride or boron carbon nitride dielectric produces a conformal layer without loading effect. The dielectric layer is formed by chemical vapor deposition (CVD) of a boron-containing film on a substrate, at least a portion of the deposition being conducted without plasma, and then exposing the deposited boron-containing film to a plasma. The CVD component dominates the deposition process, producing a conformal film without loading effect. The dielectric is ashable, and can be removed with a hydrogen plasma without impacting surrounding materials. The dielectric has a much lower wet etch rate compared to other front end spacer or hard mask materials such as silicon oxide or silicon nitride, and has a relatively low dielectric constant, much lower then silicon nitride.

FIELD OF THE INVENTION

This invention relates to electronic devices and associated fabricationprocesses. More specifically, the invention relates to depositingconformal boron nitride films that can be usefully applied as front endspacers or etch stop or barrier layers in semiconductor devicefabrication.

BACKGROUND OF THE INVENTION

Semiconductor processing involves forming Metal Oxide Semiconductor(MOS) transistors on wafers. A MOS transistor typically includes a gatedielectric and a gate electrode, a source and a drain, and a channelregion between the source and the drain. In Complimentary Metal OxideSemiconductor (CMOS) technology, transistors may typically be of twotypes: Negative Channel Metal Oxide Semiconductor (NMOS) and PositiveChannel Metal Oxide Semiconductor (PMOS) transistors. The transistorsand other devices may be interconnected to form integrated circuits(ICs) which perform numerous useful functions.

Dielectric materials have important roles in semiconductor processing.In the front end formation of MOS transistors on wafers, dielectrics areused to isolate gate electrodes, among other uses. In this regard,spacer dielectric is applied to the side surfaces of gate electrodes.Such front end gate spacers tend to be composed of silicon dioxide orsilicon nitride. However, there materials can have a high dielectricconstant (k), can be nontrivial to remove if desired, and, if depositedby PECVD, the conformality of these materials is also subject to apattern loading effect. Moderate k dielectric also finds use in back endprocessing, for example as etch stop, hard mask or dielectric barrierlayers.

SUMMARY OF THE INVENTION

The present invention pertains to a boron nitride or boron carbonnitride dielectric layer formed by chemical vapor deposition (CVD) of aboron-containing film on a substrate, at least a portion of thedeposition being conducted without plasma, and then exposing thedeposited boron-containing film to a plasma. The CVD component dominatesthe deposition process, producing a conformal film without loadingeffect. The dielectric is ashable, and can be removed with a hydrogenplasma without impacting surrounding materials. The dilectric has a muchlower wet etch rate compared to other front end spacer or hard maskmaterials such as silicon oxide or silicon nitride, and has a relativelylow dielectric constant, much lower then silicon nitride, for example.

In one aspect, the invention relates to a method of forming a dielectriclayer. The method involves receiving in a plasma processing chamber asubstrate, and forming a boron nitride or boron carbon nitride film onthe substrate. The film is formed by a process including chemical vapordeposition of a boron-containing film on the substrate, at least aportion of the deposition being conducted without plasma; and exposingthe deposited boron-containing film to a plasma.

In another aspect, the invention relates to a semiconductor processingapparatus having a plasma processing chamber and a controller havingprogram instructions for forming a dielectric layer according to theinventive method.

These and other aspects and advantages of the invention are describedfurther below and with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts important stages in a process flow for a method offabricating a strained transistor structure in accordance with anembodiment of the present invention.

FIG. 2 illustrates a simple MOS transistor architecture to show a devicecontext in accordance with which embodiments of the present inventionmay be implemented.

FIG. 3 provides a simple block diagram depicting various reactorcomponents arranged for implementing the present invention.

FIG. 4 illustrates the process sequences for made as examples of thepresent invention.

FIG. 5 depicts cross-sections of boron nitride dielectric film materialsmade in accordance with the present invention illustrating the extremecon formality of the films produced by CVD deposition.

FIG. 6 depicts plots of an infrared absorption study of dielectricmaterials made in accordance with the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in details to specific embodiments of theinvention. Examples of the specific embodiments are illustrated in theaccompanying drawings. While the invention will be described inconjunction with these specific embodiments, it will be understood thatit is not intended to limit the invention to such specific embodiments.On the contrary, it is intended to cover alternatives, modifications,and equivalents as may be included within the spirit and scope of theinvention as defined by the appended claims. In the followingdescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. The present inventionmay be practiced without some or all of these specific details. In otherinstances, well known process operations have not been described indetail in order to not unnecessarily obscure the present invention.

Introduction

The present invention relates to a boron nitride or boron carbon nitridedielectric layer formed by chemical vapor deposition (CVD) of aboron-containing film on a substrate, at least a portion of thedeposition being conducted without plasma, and then exposing thedeposited boron-containing film to a plasma. The CVD component dominatesthe deposition process, producing a conformal film without loadingeffect. The dielectric is ashable, and can be removed with a hydrogenplasma without impacting surrounding materials. The dielectric has amuch lower wet etch rate compared to other front end spacer or hard maskmaterials such as silicon oxide or silicon nitride, and has a relativelylow dielectric constant, much lower then silicon nitride.

Process

Dielectric formation in accordance with the present invention can beconducted according to a variety of different protocols involvingdeposition of a boron-containing film without plasma, followed byexposure of the deposited boron-containing film to a plasma. FIG. 1 is aprocess flow chart illustrating this general aspect of the presentinvention for formation of a boron nitride or boron carbon nitridedielectric layer. A substrate is received in a plasma processingchamber, generally in a plasma enhanced chemical vapor deposition(PECVD) reactor (101). A boron-containing film is deposited on thesubstrate, at least a portion of the deposition being conducted withoutplasma (103). Then, the deposited boron-containing film is exposed to aplasma (105). This plasma treatment densifies the film by removinghydrogen. If the as-deposited film is not boron nitride or boron carbonnitride, the plasma treatment can be conducted with a gas mixturecomposed to have the effect of converting a deposited boron-containingfilm to a boron nitride or a boron carbide nitride film. The plasma maybe off during all or just part the deposition operation, and/or may beon only when there is no boron-containing reactant in the processingchamber. The depositing and plasma treating operations may be repeatedone or more times.

The thickness of the deposited film and the duration of the plasmatreatment are such that following the plasma treatment, the resultingfilm has been completely penetrated by the plasma for densification, andto the extent that the as-deposited film is not boron nitride or boroncarbon nitride, it is converted to boron nitride or boron carbonnitride. In specific embodiments, a suitable thickness for the depositedfilm is no more than 10 Å thick, for example about 5 Å thick. Byrepeating the film deposition and plasma treatment operations, the finaldielectric layer thickness can be tailored as appropriate for specificapplications. Thickness in the range of about 10 to 1000 Å may beachieved, for example. In some specific embodiments, such as for frontend gate spacers, a dielectric layer thickness of about 50 to 500 Å, forexample about 200 to 400 Å, such as about 300 Å may be used. In suchembodiments, the dielectric layer may, then, be composed of about 5 to100, or for example 40-60, deposited and plasma treated film layers.

The source of the boron-containing film for the deposition operation canbe a boron hydride such as diborane (B₂H₆) or an organo-borane such astrimethylboron, or, for boron nitride deposition, a boron, hydrogen andnitrogen-containing species such as borazinc, or another boron precursorthat will readily decompose to metallic boron or boron carbide whenexposed to a substrate of the appropriate temperature. In general, andfor specifically noted precursors, a temperature range of 200 to 400° C.would be adequate for such decomposition to occur. In the case of anorgano-borane precursor, the carbon in the precursor molecule may beretained in the deposited boron film.

If a direct CVD boron nitride or boron carbon nitride film is desired, agas phase nitrogen source, such as ammonia (NH₃) or nitrogen (N₂) can beadded to the reactor in addition to the boron containing precursor. Or,a single precursor species with a molecular amino-borane character, suchas borazine (generically BxHyNz, a boron, hydrogen andnitrogen-containing species) may also be used.

Suitable deposition process and parameters in accordance with thepresent invention include deposition of a boron-containing film with aboron hydride or organo-borane precursor and subsequent conversion to acorresponding boron nitride or boron carbon nitride by exposure to anitrogen-containing species during post-deposition plasma treatment ofthe deposited film; direct deposition of boron nitride or boron carbonnitride with a boron hydride or organo-borane precursor and anitrogen-containing species; direct deposition of boron nitride with asingle precursor species with a molecular amino-borane character, suchas borazine; direct deposition of boron carbon nitride with a boronhydride, amino-borane or organo-borane precursor with anitrogen-containing species, a hydrocarbon and/or anothercarbon-containing process gas. Relevant deposition parameters for somespecific embodiments include a flow rate of about 1-6 L/min. for theboron-containing precursor (e.g., diborane, trimethylboron or borazineprecursor); about 1-10 L/min. for the nitrogen-containing process gas(e.g., NH₃); HFRF: about 200-1000 W; LFRF: about 200-2000 W; totalpressure: about 2-5 T. The duration of the boron-containing precursordeposition (soak) and plasma treatment can significantly impact the filmquality. Short deposition times (e.g., 5-10 sec) and longer treatmenttimes (e.g., 10-20 sec) are preferable for leakage and conformality.

Following deposition of the boron-containing film, the film is exposedto a plasma treatment. In general, the plasma is produced by acapacitively coupled plasma source. The source may operate with a singleor dual frequency at a power of about 200-1000 W HFRF, and about200-2000 W LFRF (total power for a four station tool; a single stationtool may also be used with scaled power), and a temperature of about300-500° C., for example about 400° C.

Between the deposition and plasma post-treatment, the process chambermay be purged. The purge removes any boron-containing precursorremaining from the deposition operation so that the plasma treatment canbe conducted in the absence of any precursor that would incidentallydeposit when the plasma is on and potentially degrade the quality of thedeposited film. Various purge techniques may be used, including turningoff boron-containing precursor source flow and maintaining or adding anammonia or inert gas (e.g., N₂, He, Ar) flow, either discretely orgradually; pumping down the chamber to remove all process gases; orchanging the gap between the pedestal and the showerhead to preventreaction while the process gases are unchanged. The purge may beconducted for any suitable time, for example about 5-20 sec, to ensurethat boron-containing precursor is completely removed from the reactionchamber.

In embodiments where the as-deposited boron-containing film is boronnitride or boron carbon nitride, the plasma treatment may be conductedwithout any additional process gasses present, or with an inert gas suchas He, Ar, Xe or other noble gases. In other embodiments, the plasmatreatment of such as-deposited films may be conducted with additionalprocess gasses present in order to modify the composition of the filmsfor the final dielectric produced. In yet other embodiments, such aswhere the as-deposited boron-containing film is not boron nitride orboron carbon nitride, the plasma treatment may be conducted withadditional process gases in order to convert the as-deposited film toboron nitride or boron carbon nitride.

Additional process gases involved in the post-deposition plasmatreatment may be one or a combination of: (1) NH₃, N₂, or some othernitrogen-based molecule that can react with the as-deposited film toform or increase the proportion of nitrogen in boron nitride or boroncarbon nitride; (2) He, Ar, Xe, or other noble gases; (3) hydrocarbonssuch as CH₄, C₂H₆, C₂H₄, C₂H₂, etc., to form or increase the proportionof carbon in boron carbon nitride. In some embodiments, it may bedesirable to add hydrogen (H₂) to the gas mixture as well to add anetching component. The addition of hydrogen in the deposition gasmixture of can actually lead to a film that has less hydrogen becausethe molecular hydrogen can help remove bound hydrogen from the matrix.In this way, more weakly bonded species are etched before more strongly.So, the addition of an etch component may result in a denser film.

The plasma treatment has the effect of densifying the film by removinghydrogen, for example by removing as much hydrogen as possible from theas-deposited film. Infrared absorption analysis of the B—H bond is agood indicator of the ability to remove hydrogen, as is the electricalmeasurement of the dielectric breakdown of the material. Such data ispresented below in conjunction with the description of specificembodiments or examples of the invention as evidence of the beneficialresults obtained by its use.

A pre-treatment or nucleation initiation layer may also be used prior tothe boron-containing film deposition. It has been found that an NH₃pre-treatment, for example with an ammonia plasma, can enhance theadhesion of boron nitride to materials such as copper. Another possiblepre-treatment agent is H₂. An initiation layer, such as a very thinlayer of silicon nitride or silane for example, can also be used toenhance nucleation of a low hydrogen boron nitride.

The boron nitride or boron carbon nitride dielectric resulting from aprocess in accordance with the present invention has the capacity ofbeing at least 80% and up to 100% conformal with no loading effect asthe conformality is driven by the CVD deposition process. This processalso uses plasma, and is thus capable of running at a higher depositionrate than a traditional ALD process. The dielectric is ashable, and socan be easily removed from the substrate by ashing, for example ashingconducted with a hydrogen plasma.

According to a first aspect of the invention, the boron-containing filmdeposition operation is conducted entirely without plasma. Within thescope of this aspect are several possible variations noted above,including chemical vapor deposition using a boron hydride ororgano-borane precursor, with or without a nitrogen-containing processgas or other process gases. Specific embodiments include: depositionusing a boron hydride precursor without a nitrogen-containing processgas, followed by exposure of the deposited film to a nitrogen-containingplasma (such as an ammonia plasma) for film nitridation anddensification; deposition using an organo-borane precursor without anitrogen-containing process gas, followed by exposure of the depositedfilm to a temperature sufficient to convert the organo-borane toboron-carbide or metallic boron, and a nitrogen-containing plasma forfilm nitridation and densification; deposition using a boron hydrideprecursor with a nitrogen-containing process gas such that theas-deposited film is boron nitride, followed by exposure of thedeposited film to a plasma for film densification; and, deposition usingan organo-borane precursor with a nitrogen-containing process gas suchthat the as-deposited film is boron carbon nitride, followed by exposureof the deposited film to a plasma for film densification. Other specificvariants within the general scope of the invention as described herein,for example using other process gases during the deposition and/orpost-deposition plasma treatment operations, are also possible.

Another embodiment according to this aspect of the invention involvespulsing of the plasma during the film deposition process. According tothis embodiment, a boron hydride or organo-borane boron-containing filmprecursor and a nitrogen-containing species are present in the chambertogether for at least a portion of the film deposition operation.However, the boron-containing reactant flow into the processing chamberis controlled such that a boron precursor is only present when theplasma is off. According to this embodiment, the signal gating thepulsed radiofrequency plasma source can be used to trigger an ALD valveconnected to the boron precursor source line such that the boronprecursor is only present in the chamber during the off portion of theradiofrequency cycle. In this way, no boron will be deposited during the“on” or post-treatment portion of the cycle. A suitable pulsingfrequency for the plasma in this embodiment is on the order of about 0.1to 1 Hz for example, about 0.5 Hz, and may be limited by the timerequired to charge and discharge the boron-containing precursordispensed by the valve.

Dielectrics formed according to these embodiments, without plasma duringboron-containing film deposition, will have high conformality. Theas-deposited films will have low density; the density is increased bythe post-deposition plasma treatment. These dielectric formationtechniques may be advantageously applied, for example, in circumstanceswhere a high level of conformality is a priority

According to another aspect of the invention, a pulsed radiofrequencysource is used to excite plasma in a reaction chamber in which theboron-containing precursor and a nitrogen-containing species are bothpresent during the film deposition operation. The duty cycle andfrequency of the radiofrequency source can be set such that the plasmawill completely extinguish in the off portion of the cycle. The CVDboron growth occurs in the “on” (plasma present) and “off” (no plasmapresent) portions of the cycle, while nitridation occurs only in the“on” portion of the cycle. Because the precursor is present in both the“on” and “off” portions of the pulsed plasma cycle, and a boroncontaining film will be deposited in both, the resulting film may haveless than 100% conformality and the inclusion of some level of densityloading. A suitable pulsing frequency for the plasma in this embodimentis on the order of about 1 Hz to 10 kHz, for example about 500 Hz, andis not limited by the time required to charge and discharge theboron-containing precursor dispensed by a valve into the processingchamber, but by the level of conformality required in the dielectriclayer formed. Film deposition using such a pulsing technique isdescribed, for example, in application Ser. No. 12/253,807, filed Oct.17, 2008, entitled Method for Improving Process Control and FilmConformality of PECVD Film, incorporated herein by reference for thispurpose. The more the plasma is on during boron-containing filmdeposition, the less conformal but more dense the deposited film, sothat less post-deposition plasma treatment is required to reach adesired density level. This film formation technique may beadvantageously applied, for example, in circumstances where less thanoptimal conformality is acceptable and process efficiency and high filmdensity is a priority.

A dielectric formed in accordance with the present invention film can beused as a front end of line gate spacer or back end of line hard mask,for example. This material can be removed by ashing with a hydrogenplasma and, depending upon the amount of hydrogen or carbon in thedielectric, can have a very low wet etch rate. It is thus ashable in thesame sense as amorphous carbon; however, boron nitride is also a stabledielectric which can be designed to have a low dielectric constant, lowleakage, and high breakdown voltage. This material can thus be eithersacrificial or permanent. If sacrificial, a simple hydrogen plasma canbe used to remove the boron nitride without affecting the othermaterials.

MOS Device Context

FIG. 2 illustrates a simple MOS transistor, in this case a PMOStransistor, architecture to show a device context in accordance withwhich embodiments of the present invention may be implemented. As notedabove, one suitable use for a dielectric formed in accordance with thepresent invention is as front end spacer dielectric in a MOS transistor.Referring to FIG. 2, a PMOS transistor 200 is typically composed of ap-doped substrate 202 and an n-doped well 204 within the substrate 202,which arc typically a part of an overall wafer substrate together withother transistors and devices. The p-doped substrate 202 may include anysuitable p-type dopants, such as boron and indium, and may be formed byany suitable technique. The n-doped well 204 may include any suitablen-type dopants, such as phosphorus and arsenic, and may be formed by anysuitable technique. For example, the n-doped well 204 may be formed bydoping the substrate 202 by ion implantation.

The transistor further includes a conductive gate electrode 206 that isseparated from the n-doped well 204 by a gate dielectric 208. The gateelectrode 206 may include any suitable material, such as doped orundoped polysilicon. Typically, the gate dielectric 208 is deposited inthe form of silicon dioxide, but other, for example high-k, gatedielectric materials can be also selected.

The PMOS transistor 200 also includes p-doped source 210 and drain 212regions in the n-doped well 204. The source 210 and drain 212 regionsare located on each side of the gate 206 forming a channel 214 withinthe well 204. The source 210 and drain 212 regions may include a p-typedopant, such as boron. Additionally, the source 210 and drain 212regions may be formed in recesses of the n-doped well 204.

The transistor may also include sidewall spacers 218 formed inaccordance with the present invention along the sidewalls of the gate206. The spacers 218 may be composed of boron nitride or boron carbonnitride. The source 210 and drain 212 regions and the gate 206 maycovered with a layer of self-aligned silicide (salicide) 216. A cappinglayer 120, for example composed of a compressive boron carbide covers asa blanket film the entire surface of the PMOS transistor 200.

The general manufacturing steps for fabricating PMOS transistors arewell-known in the art. Such processes may be readily adapted to formsidewall spacer dielectric in accordance with the present inventiongiven the direction provided herein.

Apparatus

The present invention is preferably implemented in a capacitivelycoupled plasma enhanced chemical vapor deposition (PECVD) reactor. Sucha reactor may take many different forms. Generally, the apparatus willinclude one or more chambers or “reactors” (sometimes including multiplestations) that house one or more wafers and are suitable for waferprocessing. Each chamber may house one or more wafers for processing.The one or more chambers maintain the wafer in a defined position orpositions (with or without motion within that position, e.g. rotation,vibration, or other agitation). In one embodiment, a wafer undergoingboron nitride or boron carbon nitride deposition and treatment inaccordance with the present invention is transferred from one station toanother within the reactor during the process. While in process, eachwafer is held in place by a pedestal, wafer chuck and/or other waferholding apparatus. For certain operations in which the wafer is to beheated, the apparatus may include a heater such as a heating plate. In apreferred embodiment of the invention, a Vector™ or Sequel™ reactor,produced by Novellus Systems of San Jose, Calif., may be used toimplement the invention.

FIG. 3 provides a simple block diagram depicting various reactorcomponents arranged for implementing the present invention. As shown, areactor 300 includes a process chamber 324, which encloses othercomponents of the reactor and serves to contain the plasma generated bya capacitor type system including a showerhead 314 working inconjunction with a grounded heater block 320. A high-frequency (HF) RFgenerator 302, connected to a matching network 306, and a low-frequency(LF) RF generator 304 are connected to showerhead 314. In an alternativeembodiment, the LF generator 304 can be connected to or located below awafer pedestal 318. The power and frequency supplied by matching network306 is sufficient to generate a plasma from the process gas/vapor. Inthe implementation of the present invention both the HF generator andthe LF generator are used. In a typical process, the HF generator isoperated generally at frequencies between 2-60 MHz; in a preferredembodiment at 13.56 MHz. The LF generator is operated generally between100-800 kHz; in a preferred embodiment at 300-500 kHz.

The description of the apparatus and respective process parameterslisted here are valid for a Novellus Sequel™ module having six stationsto deposit boron nitride or boron carbon nitride on a 200 mm wafer. Oneskilled in the art will readily appreciate that the process parametersmay be scaled based on the chamber volume, wafer size, and otherfactors. For example, power outputs of LF and HF generators aretypically directly proportional to the deposition surface area of thewafer. The power used on 300 mm wafer will generally be 2.25 higher thanthe power used for 200 mm wafer. Similarly, the flow rates, such asstandard vapor pressure, will depend on the free volume of the vacuumchamber.

Within the reactor, a wafer pedestal 318 supports a substrate 316 onwhich a highly compressive dielectric capping layer in accordance withthe invention is to be deposited. The pedestal typically includes achuck, a fork, or lift pins to hold and transfer the substrate duringand between the deposition and/or plasma treatment reactions. The chuckmay be an electrostatic chuck, a mechanical chuck or various other typesof chuck as are available for use in the industry and/or research. Thewafer pedestal 318 is functionally coupled with a grounded heater block320 for heating substrate 316 to a desired temperature. Generally,substrate 316 is maintained at a temperature in a range of about from25° C. to 500° C., preferably in a range of about from 200° C. to 400°C. to avoid thermal degradation of circuit components, such as asalicide layer, and/or for other process related purposes, as notedabove.

Process gases/vapors are introduced via inlet 312. Multiple source gaslines 310 are connected to manifold 308. The gases/vapors may bepremixed or not in the manifold. Appropriate valving and mass flowcontrol mechanisms are employed to ensure that the correct gases aredelivered during the deposition and plasma treatment phases of theprocess. In case the chemical precursor(s) is delivered in the liquidform, liquid flow control mechanisms are employed. The liquid is thenvaporized and mixed with other process gases during its transportationin a manifold heated above its vaporization point before reaching thedeposition chamber.

Process gases exit chamber 300 via an outlet 322. A vacuum pump 326(e.g., a one or two stage mechanical dry pump and/or a turbomolecularpump) typically draws process gases out and maintains a suitably lowpressure within the reactor by a close loop controlled flow restrictiondevice, such as a throttle valve or a pendulum valve. In a method inaccordance with the invention, pressures in the reaction chambergenerally are maintained in a range of about from 0.1 Torr to 30 Torr,preferably in a range of about from 0.5 Torr to 10 Torr.

In certain embodiments, a system controller 328 is employed to controlprocess conditions during the boron nitride or boron carbon nitridedielectric layer formation in accordance with the present invention, andother process operations. The controller will typically include one ormore memory devices and one or more processors. The processor mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc.

In certain embodiments, the controller controls all of the activities ofthe reactor. The system controller executes system control softwareincluding sets of instructions for controlling the timing of theprocessing operations, frequency and power of operations of the LFgenerator 302 and the HF generator 304, flow rates and temperatures ofprecursors and inert gases and their relative mixing, temperature of theheater block 320, pressure of the chamber, and other parameters of aparticular process. Other computer programs stored on memory devicesassociated with the controller may be employed in some embodiments.

Typically there will be a user interface associated with controller 328.The user interface may include a display screen, graphical softwaredisplays of the apparatus and/or process conditions, and user inputdevices such as pointing devices, keyboards, touch screens, microphones,etc.

The computer program code for controlling the processing operations canbe written in any conventional computer readable programming language:for example, assembly language, C, C++, Pascal, Fortran or others.Compiled object code or script is executed by the processor to performthe tasks identified in the program.

The controller parameters relate to process conditions such as, forexample, timing of the processing steps, flow rates and temperatures ofprecursors and inert gases, temperature of the wafer, pressure of thechamber and other parameters of a particular process. These parametersare provided to the user in the form of a recipe, and may be enteredutilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of the system controller. The signals forcontrolling the process are output on the analog and digital outputconnections of the reactor.

The system software may be designed or configured in many differentways. For example, various chamber component subroutines or controlobjects may be written to control operation of the chamber componentsnecessary to carry out the inventive deposition processes. Examples ofprograms or sections of programs for this purpose include substratetiming of the processing steps code, flow rates and temperatures ofprecursors and inert gases code, and a code for pressure of the chamber.

The invention may be implemented on a multi-station or single stationtool. In specific embodiments, the 300 mm Novellus Vector™ tool having a4-station deposition scheme or the 200 mm Sequel™ tool having a6-station deposition scheme are used. It is possible to index the wafersafter every deposition and/or post-deposition plasma anneal treatmentuntil all the required depositions and treatments are completed, ormultiple depositions and treatments can be conducted at a single stationbefore indexing the wafer.

EXAMPLES

The following examples arc provided to further illustrate aspects andadvantages of the present invention. These examples are provided toexemplify and more clearly illustrate aspects of the present inventionand are in no way intended to be limiting.

Several dielectric layers were formed by boron nitride film depositionand treatment in accordance with the present invention. Processparameters and details is are noted in Table 1, below:

TABLE 1 B2H6 Soak Conditions Pre SD Post Treat Conditions Film treatB2H6 NH3 H2 He Time Purge NH3 N2 HFRF LFRF Time Film 1 — 4125 7000 0 015 — 7000 0 0 0 5 Film 2 — 4125 7000 0 0 15 With 7000 0 750 450 5 NH3Film 3 — 4125 7000 0 0 5 With 7000 0 750 450 10 NH3 Film 4 UV 4125 70000 0 5 With 7000 0 750 450 10 SiN NH3 1 sec Film 5 — 4125 7000 0 0 5 With7000 0 750 450 20 NH3 Film 6 — 4125 7000 0 0 5 With 700 15000 750 450 10NH3

Film 1 was made by CVD boron nitride without post-deposition plasmatreatment for purposes of comparison with Films 2-6 formed in accordancewith the present invention. The remining films were conformal boronnitride deposited by CVD without plasma according to the parametersnoted in the table above, followed by an ammonia plasma post treatment.The deposition of Film 4 was preceded by deposition of a SiN initiationlayer. In each case, the deposition and the process chamber was purgedbetween the film deposition and treatment operations.

The process sequences for Films 1-4 are illustrated in FIG. 4. As notedin the description above, there are many other possible processparameters variations within the scope of the invention including theflowing of additional process and/or inert gases during the depositionand/or treatment operations, or the absence of a nitrogen containing gasduring the deposition operation.

Electrical measurements of six boron nitride dielectric materials arenoted in the Table 2 below:

TABLE 2 @ 1 MV/cm @ 2 MV/cm @ 4 MV/cm BDV Film k A/cm2 A/cm2 A/cm2 MV/cmFilm 1 4.62 1.88E-07 1.75E-05 0.0247 −2.97 Film 2 4.560 1.53E-076.03E-05 0.0784 −2.63 Film 3 4.360 4.81E-09 2.29E-07 0.0004 −4.33 Film 44.470 1.20E-09 3.17E-08 3.14651E-05   −5.31 Film 5 4.708 9.81E-109.36E-09 1.30E-05 −5.33 Film 6 4.699 1.30E-09 3.13E-09 3.40E-06 −5.78The measurements indicate low dielectric constant and reasonableelectrical breakdown and leakage. The decrease in leakage as a functionof increased plasma exposure indicates that the metallic character ofthe boron is being converted to a boron nitride dielectric. The effectof changing the duration or conditions of the plasma post treatment onthe bulk film properties of the resulting dielectric can be seen withreference to Films 5 and 6.

FIG. 5 depicts cross-sections of the first four boron nitride dielectricfilm materials illustrating the extreme conformality of the filmsproduced by all processes. This validates the notion that conformaldeposition is truly driven by the CVD deposition component and is notmodified geometrically by the plasma treatment.

FIG. 6 depicts plots of an infrared absorption study of these materialsshowing that the films are indeed a boron nitride character and that theamount of hydrogen in the film can be decreased by a modification of theprocess parameters.

CONCLUSION

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing both the process and compositions of the presentinvention. Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein.

1. A method of forming a dielectric layer, comprising: receiving in aplasma processing chamber a substrate; forming a boron nitride or boroncarbon nitride film by a process comprising, chemical vapor depositionof a boron-containing film on the substrate, at least a portion of thedeposition being conducted without plasma; and exposing the depositedboron-containing film to a plasma.
 2. The method of claim 1, wherein thedepositing and treating operations are repeated at least once.
 3. Themethod of claim 1, wherein the depositing and treating operations arerepeated a plurality of times.
 4. The method of claim 1, wherein thedeposited film is sufficiently thin to allow complete penetration of theplasma for densification of the film.
 5. The method of claim 1, whereinthe deposited film is no more than 10 Å thick.
 6. The method of claim 1,wherein the deposited film is about 5 Å thick.
 7. The method of claim 1,wherein the dielectric layer is at least 80% conformal.
 8. The method ofclaim 1, wherein the dielectric layer is a boron nitride layer.
 9. Themethod of claim 1, wherein the dielectric layer is a boron carbonnitride layer.
 10. The method of claim 1, wherein the plasma exposure isconducted in the presence of a nitrogen-containing species.
 11. Themethod of claim 1, further comprising, prior to forming the film,forming a nucleation layer on the substrate.
 12. The method of claim 11,wherein the nucleation layer comprises silicon nitride.
 13. The methodof claim 1, further comprising, prior to depositing the film,pre-treating the substrate to enhance adhesion of the film.
 14. Themethod of claim 13, wherein the pre-treatment comprises exposing thesubstrate to an ammonia plasma.
 15. The method of claim 1, wherein thefilm formation comprises chemical vapor deposition using a boron hydrideor organo-borane precursor without a plasma, followed by exposure of thedeposited film to a nitrogen-containing plasma.
 16. The method of claim15, wherein the nitrogen-containing plasma is an ammonia plasma.
 17. Themethod of claim 15, wherein the plasma further comprises a noble gas.18. The method of claim 15, wherein the plasma further comprises ahydrocarbon.
 19. The method of claim 18, wherein the precursor is aboron hydride.
 20. The method of claim 1, wherein a boron hydride ororgano-borane boron-containing film precursor and a nitrogen-containingspecies are present in the chamber together for at least a portion ofthe film deposition operation.
 21. The method of claim 20, wherein thechemical vapor deposition and plasma exposure are performed by pulsing aplasma on and off in the presence of a boron hydride or organo-boraneprecursor and a nitrogen-containing species.
 22. The method of claim 20,wherein boron reactant flow into the processing chamber is such that aboron-containing precursor is only present when the plasma is off. 23.The method of claim 20, wherein the film precursor is diborane.
 24. Themethod of claim 20, wherein the film precursor is an organo-borane. 25.The method of claim 24, further comprising exposing the precursor to thesubstrate at a temperature sufficient to decompose the precursor tometallic boron.
 26. The method of claim 25, wherein the temperature isabout 200 to 400° C.
 27. The method of claim 1, the film formationcomprises chemical vapor deposition using a boron, hydrogen andnitrogen-containing species precursor without a plasma, followed byexposure of the deposited film to a plasma.
 28. The method of claim 1,further comprising removing the dielectric layer from the substrate byashing.
 29. The method of claim 28, wherein the ashing is conducted witha hydrogen plasma.
 30. The method of claim 3, wherein the dielectriclayer has a thickness of about 50 to 500 Å.
 31. A semiconductorprocessing apparatus, comprising: a plasma processing chamber; and acontroller comprising program instructions for conducting a method inaccordance with claim 1.